注意内置类型时，使用memcpy没问题，在拷贝构造和赋值运算符重载时；
而在自定义类型时（string），必须用类型的operator=拷贝，否则会崩溃（使用了已释放的内存_ptr,调用delete时会调其析构函数）
#include<iostream>
#include<string>
using namespace std;
template<typename T>
class SeqList
{
public:
SeqList();
SeqList(const SeqList<T>& s);
SeqList<T>& operator=(const SeqList<T>& s);
~SeqList();
void PushBack(const T& data);
void PopBack();
void Print();
protected:
void _CheckCapacity(int capacity)
{
if (capacity > _capacity)
{
_capacity = capacity * 2 + 3;
Destory(_data);
_data = new T[_capacity];
}
}
void Destory(T*& _data)
{
if (_data != NULL)
{
delete[] _data;
_data = NULL;
}
}
protected:
T* _data;
int _capacity;
int _size;
};
template<class T> SeqList<T>::SeqList()
:_data(NULL)
, _capacity(0)
, _size(0)
{
}
template<class T> SeqList<T>::SeqList(const SeqList<T>& s)
:_data(new T[s._capacity])
, _capacity(s._capacity)
, _size(s._size)
{
//memcpy(_data, s._data,s._size*sizeof(T));//有副作用，如果是自定义类型的话，指针指向_ptr的是浅拷贝（释放后还使用）
for (int i = 0; i < s._size; i++)
{
_data[i] = s._data[i];//operator=
}
}
//或者形参为SeqList<T> s临时变量，交换_data,出了作用域自己释放
template<class T> SeqList<T>& SeqList<T>:: operator=(const SeqList<T>& s)
{
if (this != &s)
{
_Destroy(this->_data);
_data = new T[s._capacity];
// memcpy(_data, s._data,s._size*sizeof(T));//内置类型使用memcpy
for (int i = 0; i < s._size; i++)
{
_data[i] = s._data[i];//operator=
}
_capacity = s._capacity;
_size = s._size;
}
return *this;
}
template<class T> SeqList<T>:: ~SeqList()
{
Destory(_data);
}
template<class T> void SeqList<T>::PushBack(const T& data)
{
int capacity = _size + 1;
_CheckCapacity(capacity);
_data[_size++] = data;
}
template<class T> void SeqList<T>::PopBack()
{
if (_size>0)
_size--;
}
template<class T> void SeqList<T>::Print()
{
for (int i = 0; i<_size; ++i)
{
cout << _data[i] << " ";
}
cout << endl;
}
void Test1()
{
SeqList<int> s;
s.PushBack(1);
s.PushBack(2);
s.PushBack(3);
s.PushBack(4);
s.PushBack(5);
s.Print();
SeqList<int> s1;
s1 = s;
s1.Print();
}
void Test2()
{
SeqList<string> l;
l.PushBack("abc");
l.PushBack("dlllllllllllllllllllllllllllllef");
l.PushBack("jkl");
l.PushBack("lwdw");
l.Print();
SeqList<string> s(l);
s = l;
s.Print();
}
int main()
{
Test2();
system("pause");
return 0;
}
